1. Field of the Invention
This invention relates to a ribbon cassette having a ribbon tensioning lever associated with an end of ribbon detector; more particularly it relates to a ribbon cassette having an end of ribbon detector comprising a movable contact associated with the ribbon tensioning lever for bridging fixed contacts on the cassette holder when ribbon tension due to an end of ribbon condition pulls said tensioning lever into contact bridging position.
2. Background Art
Typewriters with associated ribbon cassettes are known e.g. from DE-U1-84 13 712.6. These known devices require expensive light barriers. Light barriers have the additional disadvantage of also reacting to contaminations or not functioning properly when contaminated. Thus, it can happen that an "end of ribbon" signal is triggered because dirt particles have interrupted the light beam, although a ribbon supply is still there. Also, according to the state of the art, in some of the devices the ribbon itself must be designed to contain certain detectable features.